Service Pack 2 for MOSS 2007, WSS 3.0 and Office 2007 will release on the 28th of April 2009. This announcements was made on the Office team blog, along with an introduction to some of the fixes / features added.

My top 6 improvements are:

Support ODF 1.1 in Office 2007 (read and Save As)

Built in Save as PDF in Office 2007 (no need to download add-in anymore)

Performance in start-up, shutdown, view rendering, and folder switch has been improved in Outlook 2007 – I have been testing this, and WOW it is a major improvement!

Substantial improvements to Forms-based authentication in WSS – I like :-)

The performance and stability of content deployment and variations feature has been improved in MOSS